The subject invention relates to a method which improves the movement of blood and other fluids and their intermixture in tubes where the surface tension is strong, and this without damage being done to the blood corpuscles. The invention also allows the use of thinner-bore tubes or less energy-consuming pumps in continuous-flow systems without change of the character of the fluids passing through systems of this kind.
In the health service, particularly in laboratories, capillary tubes are often used for collection of blood. To prevent the blood from coagulating it is customary to add double-acting solutions, i.e. anti-coagulants and thinning agents.
The strong surface tension that exists in capillary tubes causes problems in achieving inter-mixture of blood and solutions added thereto. For this reason techniques such as magnetic stirring, manual and mechanic vibrating and shaking methods are used to obtain satisfactory degrees of intermixture. However, these methods often lead to bursting of the blood corpuscles, resulting in undesirable haemolysis, which has a detrimental effect on the subsequent analysis of the blood.
Surface tension in capillary tubes may be reduced by means of various kinds of surfactants. However, surfactants too, have an haemolytical effect on blood corpuscles and interfer with other analysis reactants and therefore are used very sparingly.
Capillary tubes are also used within the health service to carry and transport blood and other fluids in so called continuous flows. In order to separate blood samples from one patient from blood samples from other patients or from other fluids which are flowing simultaneously in the same tube these fluids are separated with the aid of gas bubbles (FIG. 1).
Gas bubbles and solutions channelled through tubes of this kind are affected by the strong surface tension therein. The larger the amount of bubbles in the tubes and the longer the tube the larger the total surface tension that must be overcome. For this purpose large and energy-consuming pumps are used, e.g. peristaltically operating pumps, or else larger-bore tubes are chosen for the purpose of reducing the effects of the surface tension.